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Author Topic: Crown MA2402 amplifiers  (Read 11376 times)

aero

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Crown MA2402 amplifiers
« on: July 21, 2004, 10:01:54 PM »

I've been using MA 2402's bridged/mono for midrange in my sound system for a while. The amps are double the rated speaker power and all is well and sounding good until those pesky outdoor, hot and humid days. The 2402's seem to go into protect too early. I've got them in tight, stacked racks and put extra fans in the back as Crown recomended but still get these protect conditions. It lasts for a few moments and lowering the input generally clears it up. I sent one back to Crown for testing and 4 months later got it back with a new thermal sensor. I believe this amp still protects early.
Any suggestions?
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Elliot Thompson

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Re: Crown MA2402 amplifiers
« Reply #1 on: July 22, 2004, 09:28:06 PM »

aero
I've been using MA 2402's bridged/mono for midrange in my sound system for a while.


Elliot Thompson

So much power for mids?


aero
The amps are double the rated speaker power and all is well and sounding good until those pesky outdoor, hot and humid days. The 2402's seem to go into protect too early. I've got them in tight, stacked racks and put extra fans in the back as Crown recomended but still get these protect conditions. It lasts for a few moments and lowering the input generally clears it up.

Elliot Thompson

I own a few 2400's, and, if the amplifier shutsdown,
the ODEP light is generally not lit. Upon ODEPing,
the output power is reduced signicantly. If you reduce
the gain and the amplifier comes back on, I would imagine
it is still ODEPing.

The Obvious Questions Comes To Mind:

Are You Cleaning Your Filters?

How Many Speakers Are You Loading On The 2402 In
Bridged Mode?

What Is The Nominal Impedance Of Each Speaker?

Are You Feeding 20 Amps Per 2402?

Do You Have The External Fans Attached To The Back
Of The Rack In The Exhaust Direction?


aero
I sent one back to Crown for testing and 4 months later got it back with a new thermal sensor. I believe this amp still protects early.
Any suggestions?

Elliot Thompson

Protects Early? Please explain. By your last comment, it
sounds like you can't provide enough current for the amplifier
when driven in bridged mono mode.
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Elliot

Ronnie Blenden

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Re: Crown MA2402 amplifiers
« Reply #2 on: July 23, 2004, 01:27:55 AM »

I have used crown macrotechs for quite a while as well, but i am also one of the non believers in running bridge mono at 4 ohm.  I have never ever had any crown amps overheat and go into protection with me when running at 4 ohm stereo/ 8 ohm brige mono.  However when the show gets going loud and proud, especially on mids where there is an almost constant dynamic level of sound then they would not hold up in a 2ohm stereo/4ohm bridge situation.  You would not notice protection if they were on your subs since it is a highly transient response but you might start to notice a mushy kick drum.
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aero

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Re: Crown MA2402 amplifiers
« Reply #3 on: July 23, 2004, 03:33:20 PM »

Elliot,
My usage of "protect" in this case means "ODEP". The filters are kept very clean, the amps are kept in the shade. I drive a 4 ohm load which is the Crown rating in bridged mono. This means two 8 ohm cabs (midrange only) in paralell. I've tried separate 20 amp circuits to no avail and run the fans both ways. Crown recomends exhaust from the back so that's how they are now but last 4th of July I had the same problem. I have countered it a bit by reducing the gain to the system and increasing the crossover to the subs to 120 Hz. This gets me a bit more but I don't get the response I'd like. The reason I use so much midrange power is to avoid pushing the amps to their limit and run them cooler (just a theory). They drive EAW LA460's where the midrange is a 15" and 6" passively crossed in the box.
How can I provide more current for the amps?
aero
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aero

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Re: Crown MA2402 amplifiers
« Reply #4 on: July 23, 2004, 03:52:32 PM »

"Loud and proud" is exactly when these amps seem to flake out. The alternative within the Macrotech line is use MA5000's which for me is not practical and very expensive or use one 2402 per pair of speakers. I hope that isn't required 'cause they should be able to work the way I'm using them!
aero
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Elliot Thompson

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Re: Crown MA2402 amplifiers
« Reply #5 on: July 23, 2004, 05:41:41 PM »

aero
Elliot,
My usage of "protect" in this case means "ODEP". The filters are kept very clean, the amps are kept in the shade. I drive a 4 ohm load which is the Crown rating in bridged mono. This means two 8 ohm cabs (midrange only) in paralell.

I've tried separate 20 amp circuits to no avail and run the fans both ways. Crown recomends exhaust from the back so that's how they are now but last 4th of July I had the same problem. I have countered it a bit by reducing the gain to the system and increasing the crossover to the subs to 120 Hz. This gets me a bit more but I don't get the response I'd like.

Elliot

Okay. I think I see the problem here. By you having your
Crossover settings (Midrange) set lower than 120Hz, you
want more midbass out of these LA 460's.

Which is fine. However, each 460 is dipping below its
nominal rating (8 ohm) once you have the Crossover
settings below 120Hz. So in theory you are driving
two 8 ohm loads, but in reality, you are pushing
a much lower impedance. All speakers have unstable
impedances, especially, in the bass region.

I'm betting this is the problem. One of those LA 460's
may indeed have an impedance dip of 5 - 4 ohms.

In the case of using two in parallel mode, the dip
could be anywhere from 2.5 - 2 ohms. Which exceeded
the Macrotech's 4 ohm Minimum capacity in
Bridged Mode.

Come to think of it, I'm more than certain this is
whats happening.

aero
The reason I use so much midrange power is to avoid pushing the amps to their limit and run them cooler (just a theory). They drive EAW LA460's where the midrange is a 15" and 6" passively crossed in the box.

Elliot

Ah... But, the problem here is, due to the amp is in ODEP
mode, you are not getting 2000 watts out of each 2402. You
are more than likely getting much less. For the whole idea
of ODEP is to reduce the output to prevent the amp from
shutting down. Actually, you are driving the amp harder
this way, than if you ran them in stereo mode.

I've never used the LA 460 before. However, looking
at their published specs on EAW's site, the LA 460
in passive mode is 97 dB. That's very low, and, now
I understand why you are feeding them so much power.
Also, since you like more midbass, if you could get
your hands on some KF 850's it would make a bigger
difference.The 15 is housed in a horn and will give
you 102 dBs vs 97 dB.

What you could do is rent a MA 3600 and put one
box a channel, stereo mode. This amp will give you
the same power at 8 ohms stereo, as the 2402 would
deliver in 4 ohms bridged. So, you could reduce the
Crossover lower than 120Hz, and, not fear of the
amplifier shutting down. However, being the 3600
that it is, it has a reputation of destroying drivers
when overdriven. So, you'll need to brickwall the signal
to prevent this from occuring. Of course you could
go for the 5000 and run two boxes aside in stereo
mode as well.

If it was me I would just dump the LA 460s and,
get my hands on some used KF 850s or any other
box that offers a horn-loaded 15. Considering
these boxes offer such a low sensitivity in
the mid - low midrange section.

Best Regards,

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Elliot

aero

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Re: Crown MA2402 amplifiers
« Reply #6 on: July 24, 2004, 07:28:56 AM »

The impedance problem is something I discussed with the Crown service guys long ago and they didn't really think it was a problem. I believe their ratings use the term "nominal" and the amps can deal with some fluctuations. However, a single problematic driver is a good idea. I'll have to check all 10 of the cabs I have and that won't be fun.
I figured I wouldn't need the full 2000 Watts out of this amp configuration. The speakers would over-excurt before I reached this output power. That is not happenning. So if ODEP limits the output power can it be cutting by 1000 Watts when hot? Seems unlikely. The trouble with using them in stereo mode which I did at first was 1 cab, 1 amp channel, i cable. I needed way too much cable and too many amps for this to be a practical system for my jobs. Sure, some 850's or Meyer MSL's but gear and crew and a bigger truck are expensive. I can move and set-up this system nearly alone.
Thanks for the insight, I'll start impedance checking (never thought to do that as a regular maint. thing).
aero
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Elliot Thompson

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Re: Crown MA2402 amplifiers
« Reply #7 on: July 24, 2004, 09:18:40 AM »

aero
The impedance problem is something I discussed with the Crown service guys long ago and they didn't really think it was a problem. I believe their ratings use the term "nominal" and the amps can deal with some fluctuations.

Elliot

Sure. They can handle some fluctuations. However, if the
impedance dips too low its going to cut back the power.
Thats the concept behind ODEP. Instead of shutting down
like the majority of amplifiers do, ODEP will just reduce
the output. Think compression here. The more signal you
feed it, the lower the output is reduced.


aero
However, a single problematic driver is a good idea. I'll have to check all 10 of the cabs I have and that won't be fun.

Elliot

I think some confusion is starting here. The driver is
not defective. Its the way how the driver reacts in the
enclosure. All speakers experience this. This is why
you generally find regional tour companies, playing at
4 ohms per channel in stereo mode minimum. Its to ensure
the amplifier can play under the worse case scenerio,
when you are driving them at volume 11.

To make your life easier, just request the impedance curve
sheet for the LA 460 from EAW. Its a ballpark estimate, and,
will give you a general idea where the LA 460 stands under
the given frequency.

Actually, you would really need to have the proper tools
to literaly measure the impedance curve on how the speakers
corelate in the enclosure.

aero
I figured I wouldn't need the full 2000 Watts out of this amp configuration. The speakers would over-excurt before I reached this output power. That is not happenning. So if ODEP limits the output power can it be cutting by 1000 Watts when hot? Seems unlikely.

Elliot
I agree. Take the old 4 rack space Peavey CS 800 for example.
The spec sheet states 460 watts per channel @ 1Khz, 1% THD.
At 2 ohms per channel, the amplifier wattage reduces to 250
watts. This is because the amplifier is limiting the output
to prevent overheating, and, premature shutdown. In the case
of the MA 2402, the ODEP is doing the same thing.

It will reduce the output low enough so the amplifier won't
shutdown. Whether its 1000 watts or 5 watts, it depends on
how hard you are driving the amplifier when the impedance
of the speakers are dipping below the amplifiers minimum
load, when driven at high SPLs.

aer
The trouble with using them in stereo mode which I did at first was 1 cab, 1 amp channel, i cable. I needed way too much cable and too many amps for this to be a practical system for my jobs. Sure, some 850's or Meyer MSL's but gear and crew and a bigger truck are expensive. I can move and set-up this system nearly alone.

Elliot
I hear dude. I'm a one man army myself. You could operate the
amplifier in Parallel Mono. In this mode, the minimum impedance
is 1 ohm, and, you could load two cabs using one speaker cable.

Keep in mind that Crown's MA/MT/PB/PT/CT/ parallel mono is
not considered what QSC, and, Crest considered parallel mono.

If you refer to the MA 2402's manual, it will tell you
how to configure the amplifier to handle a 1 ohm load.

Using it in this fashion, increases the 2402's current,
thus handling 1 ohm. Oppose the Bridge Mono method, which
increases more voltage, offering 4 ohm minimum.

I can understand the money you've invested in this rig,
and, you can't just upgrade so easily. This is why, I'm
giving you more alternatives.

Best Regards,
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Elliot

aero

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Re: Crown MA2402 amplifiers
« Reply #8 on: July 24, 2004, 02:19:25 PM »

Thanks for the paralell mono suggestion. I will check this out. I find it strange that my cheaper Crest CA series amps don't have any quirks to deal with through all of the punishment the've seen. Hmmm.
Anyway, thanks for the advice, I'll get to work on it and let you know.
Regards,
aero
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Elliot Thompson

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Re: Crown MA2402 amplifiers
« Reply #9 on: July 25, 2004, 06:57:02 PM »

Its Funny you mentioned Crest.

I was evaluating the CA 9 -vs- the 7001's
power supply. Found out that the CA Series
uses the same overbuilt power supply as the
Professional Series.

In case you don't know, Crest is nortorious
for their oversized power supply.

This is why their amps weigh a ton Very Happy

Yeah, the Parallel Mono scheme should remedy
the problem.

Best Regards,

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Elliot

aero

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Re: Crown MA2402 amplifiers
« Reply #10 on: August 23, 2004, 07:49:14 PM »

Elliot,
It took a while but I finally had the "big" system out last weekend and got to try your paralell mono idea. It seems to have done the trick. It was not a hot or humid, long and gruelling day for the amps but it was a large audience area and everything was cranked for about 4 hours. No ODEP conditions or distortions and the system was louder. There is one remaining problem which I'll discuss with Crown. I use their IQ PIP USP2 modules in two of the ampifiers. One USP2 for high crossover and the other USP2 for low crossover (in one 2402). The processed 2402 amp processes in stereo but amplifies in mono (formerly bridged mono). The channel 2 processed signal is routed to another amp. In paralell mono the channel two, processed output is missing. I worked around it by leaving that amp in stereo. Its really a question for Crown as my literature isn't comeplete enough to show where the signal input chain is broken when paralell mono is used.
Anyway, thanks for the help, I'm almost a happy man.
aero
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Elliot Thompson

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Re: Crown MA2402 amplifiers
« Reply #11 on: August 24, 2004, 09:20:48 AM »

Thats Great!

So my assumptions were correct about losing volume
due to the impedance drop.

Just keep in mind, Powerbase, Powertech, Comtech,
Microtech, & Macrotech all include the parallel
mono scheme. Just in case you happen to come across
one, and, need to go below 8 - 4 ohm minimum bridge
mono scheme.

Glad to hear everything worked out for the best.

As for PIP issue, it would be best (As you mentioned)
to relay the question to Crown. Although I use
Crown amps, I never used their PIP modules. So,
I couldn't give you any feedback on them.

Best Regards,
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Elliot

rubbermatch

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Re: Crown MA2402 amplifiers
« Reply #12 on: September 06, 2004, 08:20:47 PM »

I just put one 2402 per LA325 and parallel mono 'd them and voila! Now I can hear the subs farting.
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aero

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Re: Crown MA2402 amplifiers
« Reply #13 on: September 07, 2004, 06:15:11 PM »

Elliot,
I had a chat with a Crown Tech. and he confirmed the whole parallel mono issue. Any impedance dips below 4 ohms are problematic. This is not what a previous Crown tech. said long ago. He said that those ratings were "nominal" and weren't the cause of my problems. Anyway, this guy was good. He even told me about a low cost 20mA current loop converter from Blackbox that will allow me to interface with their IQ system. I'll need it to program the extra PIP card I need to make this all work.
Thanks again.
AERO
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Elliot Thompson

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Re: Crown MA2402 amplifiers
« Reply #14 on: September 11, 2004, 08:30:29 PM »

Yeah.

Those stuff happen. Do yourself a favor, and,
read the MA 2402 manual, from front to back.

It seems like Crown won't be offering so much
information in their amplifier manuals any
longer. Their new models basically, tells you
the A B C's, and, thats it.

Seeing that the Macrotech is a 20+ year design,
I would imagine a few representitives from Crown's
Tech Service will not be as familiar with them
like the CE 4000.

And with the I Tech being the new Top Of The
Line, I really doubt they are training the
new staff on the Macrotech Series.

The Parallel Mono scheme is not on their
K, CE, XS, nor I Tech series. So, given
another 10 years from today, the new techs
may not have a clue why the IOC light, stays
lit when it is in Parallel Mono mode.

Best Regards,



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Elliot
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